Osmotic wound drain

ABSTRACT

An evacuator device for the extraction of body fluids is comprised of body fluid receiving members adapted to be inserted into the area of the wound and fabricated from membrane material exhibiting controlled permeability to water, and a compartment for collecting such water that flows by osmosis across said membrane in a tendency for osmotic equilibrium with the environment of the device. The body fluid receiving means are advantageously elongated tubes adapted for insertion into the human body.

United States Patent 1191 Stepno Apr. 29, 1975 1 OSMOTIC WOUND DRAIN[75] Inventor: Norman Howard Slepno.

Alexandria, Va.

[73} Assignee: Alza Corporation. Palo Alto, Calif [22] Filed: May 22,1972 [2]] App]. N0.: 255,438

[52] US. Cl. 128/276 [51] Int. Cl A61m 1/00 [58] Field of Search128/260. 276. 278, 214 R [56] References Cited UNITED STATES PATENTS3.115.138 12/1963 McElvcnny et al 4. 128/278 3.732.865 5/1973 Higuchi cta1. 128/260 3.760.804 9/1973 Higuchi ct a1. 128/260 3.760.805 9/1973Higuchi 128/260 Leepcr 128/260 Theeuncs 128/260 X PrimaryEraminer-Richard A. Gaudet Assistant Emminer-J. C. McGowan Anorney,Agent, or Firm-Bacon 81 Thomas [57} ABSTRACT An evacuator device for theextraction of body fluids is comprised of body fluid receiving membersadapted to be inserted into the area of the wound and fabricated frommembrane material exhibiting controlled permeability to water, and acompartment for collecting such water that flows by osmosis across saidmembrane in a tendency for osmotic equilibrium with the environment ofthe device. The body fluid receiving means are advantageously elongatedtubes adapted for insertion into the human body.

8 Claims, 3 Drawing Figures OSMOTIC WOUND DRAIN FIELD OF THE INVENTIONThis invention relates to a device for evacuating fluids from the humanbody, especially from the area of a wound. More particularly, thisinvention relates to a simple economical evacuator which employs theprinciple of osmotic diffusion to remove body fluids from the area of awound.

BACKGROUND OF THE INVENTION It is a relatively common surgical procedureto provide for the draining or evacuation of body fluids from the areaof a wound or incision incurred during surgery for prevention of fluidbuild-up, to combat suture pressure, infection, and the like. Ordinaryoperative wounds are normally drained for a period of about 48 hoursafter the operation. Some operations, being more extensive and/orrequiring more extensive procedures, result in a large build-up of bodyfluids in the wound area which, as dictated by normal medical practice,should be removed to promote safe, speedy healing.

Typical examples of surgical operations which require the removal ofbody fluids from the wound area during healing are as follows: (I)operations such as radical breast and neck dissections, abdominal,perineal, and certain chest procedures; (2) evacuating hematoma in suchoperations as upon the hip, femur, tibia, forearm or hand; (3) knee andankle joint operations and the like; (4) compound fractures; (5) thetreatment of large soft tissue abscesses, and the like; (6) treatment ofchronic osteomyelitis and septic joints; and (7) various other uses.

The use of effective measures to withdraw fluids which accumulate in thearea of the wound or incision in such operations results in a number ofimproved conditions. Swelling is kept at a minimum and suture tension ismarkedly decreased with noticeably less postoperative pain, and thewound edges are kept white, flat, and quiescent. The elimination ofhematoma, swelling, and tension also eliminates some infection promotingfactors.

U.S. Pat. No. 3,l l5,l38 to McElvenny et al. describes a wound draindevice which operates under the principle of applying a negativepressure. In that patent, a device for creating negative pressure islocated outside of the body and conncted to tubular means located in thewound area. The pressure acts to withdraw the fluids from the area ofthe wound and prevents the accumulation of same. While such a device hasbeen found to be an acceptable means to prevent the accumulation of bodyfluids in the wound area, representing a marked advance over thetheretofore known electrical or mechanical evacuators, the manufactureof this prior art device requires certain rigid standards which must beadhered to in order that the device work effectively as desired. Forexample, the McElvenny et al. device requires that the tubing locatedwithin the body in the wound area have openings therein which connect tothe central core for evacuation of the body fluids to the collectionmeans. It is ofcourse obvious that should any of these openings occuroutside of the body, the negative pressure being applied would benegated by the introduction of air from the atmosphere. Consequently,the openings in the tubular member or members of the McElvenny et al.device must all be located within the body surrounding the wound area.Furthermore, the only means by which the body liquids may be removedfrom the wound area is through these openings and if accumulation ofbody fluids occurred at other areas surrounding the tube, the devicewould not operate to remove such liquids. Also, the collection means orevacuation unit of this prior art device acts as a pump which requirescertain specified and rather complex construction features includingtension means located around the inside of the pump for applyingpressure to the top and bottom of the unit in order that the negativepressure desired may be produced. The top and bottom portions of theevacuating unit of this prior art device moreover require internallydisposed shoulders for maintaining the springs in operative position. Itcan be seen, therefore, that while the McElvenny et al device fordraining wounds by the application of negative pressure does result in adegree of effecienty in removing body fluids from the area of the wound,it would be desirable to obtain the same or improved result with a moresimplified device.

SUMMARY OF THE INVENTION Accordingly, it is a primary object of thisinvention to provide a device for evacuating fluids from the human body,especially from the area of a wound or incision, which device operatesin a simple and efficient manner.

It is another object of this invention to provide a device forevacuating body fluids from the area of a wound or incision by theapplication of the principle of osmosis.

It is a still further object of this invention to provide a device forthe evacuation of body fluids from the area ofa wound or surgicalincision which is simple and efficient in operation and which is easilyadapted for use by ambulatory patients.

These and other objects will become apparent from the description givenhereinafter.

Briefly, in accordance with this invention, there is provided a devicefor evacuating body fluids which comprises a conduit member,advantageously tubular, comprised of a material having controlledpermeability to water, said conduit member being connected to acollection means or container compartmentalized by means of a flexiblewater impervious diaphragm. The first compartment of the collectionmeans, to which the conduit member is connected, contains a solution ofan osmotically effective solute which exhibits an osmotic pressuregradient against water, and the conduit member contains a like solution.Means are also provided for attaching the collection means firmly to thebody, and in the desired position, for use on ambulatory patients. Theconduit member is adapted to be inserted into the body in the area ofthe wound or incision, whereby water of the body fluids, by osmosis,diffuses into the tubular means and passes into the collection meanscausing the flexible diaphragm to expand upon water uptake into aninitially empty space or second compartment in the collection means.

In another aspect of this invention, the first compartment of thecollection means contains two solutions of osmotically effective soluteseach exhibiting an osmotic pressure gradient against water, one beingmore concentrated than the other, and said solutions themselves beingphysically separated within the said first compartment by means of asemipermeable membrane. The less concentrated solution also fills theconduit member and that portion of the collection means to which saidconduit is connected. The more concentrated solution causes excess waterto pass from the less concentrated solution into the chamber containingthe more concentrated solution and causes a flexible diaphragm to expandinto an initially empty area or second compartment of the collectionmeans.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view, partially incross-section, of the wound drain device of the present invention.

FIG. 2 is a plan view partially in crosssection, of the modification offrom a device of the present invention in which the container hasadditional means for separating a less concentrated osmotic solutionfroma more concentrated osmotic solution by means of a semipermeablemembrane.

FIG. 3 is a view of a front portion of a human body illustrating theapplication of the present invention thereto in a radical breastdissection or breast removal.

DETAILED DESCRIPTION OF THE INVENTION One embodiment of this inventionis illustrated in FIG. 1. While FIGS. 1, 2, and 3 all show two tubularconduit members for insertion into the area ofa wound or incision, it isto be understood that one tubular member will in some cases suffice,especially in those operations in which the accumulation of body fluidis slight; it is also envisioned that in some instances more than twoconduits or tubes can be employed. Likewise, the tubular members asillustrated in the drawings can be connected to each other via anintermediate portion which in effect would result in one tubular memberconnected to the collection means. While a Y-shaped connection means isillustrated in the drawings, it will be appreciated that in the case ofthe use of one tubular member such a connection means would beunnecessary, and, in fact, the tubular member or members may be directlyconnected to the collection means, if desired.

Referring specifically to FIG. 1, tubular members 2, comprised ofmaterial exhibiting controlled permeabil ity to water and which containa solution of an osmotically, effective solute which exhibits an osmoticpressure gradient against water and body fluids, are connected via aconnector 3 to collection means 4. Of course, both tubular members 2 andconnectors 3 are completely filled with the solution of the osmoticallyeffective solute in order to establish the osmotic pressure differentialacross the membrane of which the tubular members 2 are composed. Thetubes 2 are advantageously comprised of semi-permeable, anisotropiccellulose acetate membrane material of the type used in reverse osmosiswater desalination. Connection means 3 is illustrated as being Y-shapedhaving connectors 9 and for connection with tubular means 2 andcollection means 4 via lead-away tube 4a, respectively. Connectors 9 and10 are conveniently of the friction grip type. Collection means 4,advantageously a simple plastic flask, is compartmentalized intocompartments 5 and 6 by means of flexible water impervious diaphragm 7.Compartment 6 is initially empty to allow for the expansion therein offlexible diaphragm 7, e.g., to the position exemplified by 7a.Compartment 5 is completely filled with solution 1 of the osmoticallyeffective solute, which solution likewise completely fills the tubularmembers 2 which are sealed at their distal ends.

Plug means 8 is provided for emptying and filling the compartment 5.

FIG. 2 shows a device similar to that illustrated in FIG. 1 with tubularmembers 12 again being connected via Y-shaped connector 13 to collectionmeans 14. The connection means 13 are connected via connectors 20 and 21to tubular members 12 and lead-away tube 14a, respectively. Again, theseconnectors are preferably of the friction grip type. Collection means 14is in this embodiment divided into compartments l5, l7 and 18, withcompartments l5 and 17 being separated by means of semi-permeablemembrane 16, or other material exhibiting controlled permeability towater. Compartment 18 is initially empty and is separated from theremainder of the collection means 14 by means of water imperviousflexible diaphragm 19. Compartment 15 contains a solution 11 of anosmotically effective solute which exhibits an osmotic pressure gradientagainst water, e.g., normal saline, and which is likewise containedwithin the confines of tubular members 12 and also connector means 13.Compartment 17 contains a more concentrated solution of osmoticallyeffective solute and, in use, water from solution 11 passes throughsemi-permeable membrane 16, by osmosis, into the compartment 17, thuscausing this compartment and flexible diaphragm 19 to expand, e.g., tothe position exemplified by 190. An amount of water corresponding to thevolume increase in the compartment 17 also flows from the body, byosmosis, across the membrane comprising the tubes 12 and into theevacuator. Plug means 22 and 23 are provided for the addition orsubtraction of materials to sections 15 and 17, respectively.

FIG. 3 illustrates the application of the invention to a breastoperation. Tubular members 2 are inserted into the wound or incisionarea exactly as in the McElvenny patent and are operatively connected tocollection means 4 via Y-shaped connector member 3. The collection means4 is firmly strapped to the body via straps 32 attached to collectionmeans 4 by means of, e.g., flaps 31. Straps 32 may be adjusted by buckleor snap means 33.

In operation of the device of this invention, with reference to FIGS. 1and 3, prior to suturing of the wound, the tubes 2 are inserted into thewound as in the McElvenny patent and connected to collection means 4 viaY-shaped connector 3. Sealing means 9 hold tubes 2 in a water tightfriction grip and sealing means 10 holds lead-away tube 40 in the samemanner. As shown at FIG. 3, the tubular member, or members, arepreferably not brought out through the incision 30 but rather at a pointor points spaced therefrom, whereby the tube or tubes pass throughhealthy tissue from which, following completion of the drainage, thetube or tubes may be withdrawn leaving a small opening which willreadily heal.

Water, from the objectionable body fluids in the area of the wound,diffuses or is removed from the said area of the wound, by osmosis, intothe interior of tubular members 2 in a tendency towards establishing anosmotic equilibrium in the system. The tubes 2 contain a solution of anosmotically effective solute which exhibits an osmotic pressure gradientagainst water. Inasmuch as body fluids are composed of approximately 98water, essentially all of the body fluids will be transferred from thearea of the wound into the interior of tubular members 2, which membersare comprised of osmotic membrane material. This permeation of watercauses a corresponding and ultimate increase in the volume of theosmotic solution in compartment 5, which increase in turn results in anexpansion of diaphragm 7 into (e.g., to the position shown as 70) theintially empty chamber 6. The osmotic solution 1 in compartment 5 andtubes 2 is preferably a saturated aqueous salt solution. To maintain thesolution saturated and therefore to achieve a constant osmotic pressurethroughout operation of the evacuator, the compartment containing thesolution also contains excess solute in solid form. If desired,additional solute may be added to and/or some of the osmotic solutionmay be removed from compartment 6 by removing plug 8.

The modification of the device, illustrated in FIG. 2, operates in asimilar manner, i.e., water, from the wound area passes by osmosis fromthe body into semipermeable tubes 12, through connector 13 and intocollection means 14. In this modification the top section of collectionmeans 14, i.e., the area above flexibie diaphragm 19 (which correspondsto the diaphragm 7 of FIG. 1), is divided into two additionalcompartments l5 and 17, by means of a semi-permeable membrane 16. A lessconcentrated solution of osmotically effective solute, e.g., normalsaline, is placed in compartment l5 and tubes 12, and a moreconcentrated solution of osmotically effective solute is placed incompartment 17. Since the concentration of the solution in compartment17 is greater than the concentration of the solution in compartment 15,water is caused to diffuse, by osmosis, from compartment 15 throughsemipermeable membrane 16 into compartment 17, since, in relation to thesolution in compartment 17, the solution in compartment 15 is hypotonicand, conversely, in relation to the solution in compartment 15, thesolution in compartment 17 is hypertonic. This passage of water frombody fluids into compartment 15 and thence ultimately into compartment17 results in the concentration of the solution in compartment 15 and intubes 12 being maintained substantially equal and sufficiently high tocause body liquids from the wound area to diffuse into the tubes andpass to the collection means 14. As the volume of the concentratedsolution in compartment 17 increases with water uptake, flexiblediaphragm l9 correspondingly expands into initially empty space 18,e.g., to position [90. Solution, solute or solvent may be added to orremoved from compartments l5 and 17 by removing plugs 22 and 23,respectively. In the modification as illustrated in FIG. 2, the solutefrom the saturated osmotic solution located in compartment 17 does notleave or migrate from the confines of said compartment since it is notnecessary for this solution to be present in the interior or tubes 12,and yet since this solution continuously removes water from the solutionin compartment 15 and tubes 12, it acts effectively to promote theremoval of the body liquids from the wound area. The device of FIG. 2,therefore, is characterized by the phenomenon that all of the pumping"is done at the pump itself, i.e., across the membrane 16, rather thanwithin the body. And in this instance there is no problem whatsoeverwith salt transport within the tubes 12. in the FIG. 1 embodiment thediffusive flux of the osmotically effective solute towards theextremities of the tubes 2 must be of such velocity as to preventdepletion of such solute therein.

The device of this invention is, of course, suitable for bed patientsbut a particularly desirable feature of the device of this invention isits suitability for ambulatory patients. As shown in FIG. 3, the devicemay readily be secured to the patients body allowing for a wide range ofmovement without giving rise to the patients discomfort or affecting theoperation of the wound drain device. After the insertion of thesemi-permeable tubes 2 into the wound area as in McElvenny andconnection thereof to collection means 4, in the manner described above,the collection means is strapped onto a suitable position of thepatients body via means such as mounting flaps 31 and straps 32. Such anarrangement results in only minor restrictions on the patients movementsand when the draining of the wound is finished, tubes 2 are removed anddiscarded along with collection means 4.

While semi-permeable tubular means 2 or 12 may be directly connected tocollection means 4 or 14, respectively, in any suitable manner, it ispreferred, as illustrated, to employ intermediate connector means 3 and13. The material employed for connection means 3 and 13 need not besemi-permeable and in fact, it is preferred that this portion of thedevice of this invention be composed of a material that is notsemi-permeable to water. Suitable materials for use in the constructionof connector means 3 or 13 would be obvious to those skilled in the artand may be natural or synthetic rubber, polyethylene, polypropylene,vinyl, and other like plastic materials. Likewise, the lead-awaymembers, 4a and 14a, from the collection means may themselves byY-shaped for receiving tubular members 2 and 12, respectively. The onlyrequirement for the connection means is that it be adapted to suitablygrip tubular means 2 or 12 and/or lead-away means 40 and 14a in asuitable friction-type manner to allow the passage of liquid from thetubes 2 and 12 to their respective collection means.

It can be seen that the device of the present invention operates toremove fluids from the area about a wound by osmosis, that is, diffusionof the water from the ex cess body fluids into the interior of thesemi-permeable tubing members. Since the body fluids in a human body arecomposed of approximately 98% water, the tubular semi-permeable membersare placed in a hypotonic aqueous environment. The osmotic solutionlocated within the interior of the tubular members being correspondinglyhypertonic causes water, by osmosis, to be diffused into the interior ofthe tubular members since it is a well recognized priciple of osmosisthat a hypertonic solution tends toward equilibrium, that is,isotonicity. Note especially the embodiment of FIG. 1. In this manner,water is readily removed from the area of the wound and collected at apoint outside of the body.

It is possible to determine the flux or diffusion of body liquidsthrough the semi-permeable tubing by Ficks Law of Diffusion. Assumingthat it is desired to ,remove lSO ccs of body fluid per day and alsoassum- [0" sec X [5 cm cm sec This amount of flux or difiusion canreadily and easily be achieved with common osmotic membranes such ascellulose acetate. In order to provide an even greater surface areaavailable for osmotic diffusion according to the invention, it iscontemplated that the tubes 2 and 12 can be fluted or of a star orsimilar configuration in cross-section.

The tubular members can be formed from a wide variety of materialspermeable or semi-permeable to sol vent (water) but not to solute, i.e.,those suitable for the construction of an osmotic cell. For bestresults, the membrane should be substantially impermeable to passage ofthe osmotically effective solute so as to prevent loss thereof. Typicalmembranes are isotropic membranes such as unplasticized celluloseacetate, plasticized cellulose acetate, reinforced cellulose acetate,cellulose diand tri-acetate. ethyl cellulose; anisotropic reverseosmosis membranes which typically are made of cellulose acetate;silicone rubbers, polyurethanes, natural rubber, and hydrolyzedethylene/vinyl acetate copolymers. Isotropic membranes have less waterpermeability than do the anisotropic membranes. Also, with both type ofmembranes, increasing the acetate content of the cellulose acetatepolymer decreases the water permeability. Since, as stated above, it isoften important for rapid removal of body liquids from the wound area,membranes allowing relatively rapid water transmission, i.e.,anisotropic membranes, are the preferred. A cellulose acetate membranesuitable for this application is available from Eastman ChemicalProducts. It is of course obvious that the material employed for thesemi-permeable tubing should be compatible with human biological tissuesso as to avoid irritation, infection, or other complications.

There are likewise a wide variety of osmotically effective solutes, thatis, those which, when in solution, exhibit an osmotic pressure gradientagainst water, which can be used in the device of this invention. Theseinclude magnesium sulfate, magnesium chloride, sodium chloride,potassium sulfate, sodium carbonate, sodium sulfite, sodium sulfate,sodium bicarbonate, potassium acid phthalate, calcium bicarbonate,potassium acid phosphate, raffinose, tartaric acid, succinic acid,calcium succinate, calcium lactate, magnesium succinate, and the like.The excess solute in solid form located within the chamber containingthe saturated osmotic solution can be in the form of dispersed particlesor perferably in the form of a pellet. This solution can initially be asolution of the same or of a different osmotically effective solute thanthe solid excess solute. A particularly effective osmotic solute hasbeen found to be magnesium sulfate, or epsom salts.

The collection means into which the water from the body fluids pass viathe semi-permeable tubes, i.e., collection means 4 in FIG. 1 andcollection means 14 in FIG. 2, can be formed of polystyrene,polyethylene, polypropylene, polyvinyl chloride, reinforced epoxy resin,polymethyl methylacrylate, styrene/acrylonitrile copolymer, polyamides,polyesters, and other like plastic materials, as well as natural andsynthetic rubbers, and metals such as sheet metals (aluminum, copper,steel, etc.). it is of course intended that such collection means act asa barrier to the transport of water and osmotic solution. The diaphragmused to separate the compartments of the collection means must beflexible in order to allow for the increase in volume of the osmoticsolution. Suitable materials for use as the flexible diaphragm arenatural or synthetic rubbers and certain sheet polyurethanes which areimpervious to the passage of water and other liquids. The connectionmeans 3 and 13 may be made from the same materials mentioned in regardsto the collection means 4 and 14. It is not necessary that they be ofthe same material although in most cases it will be preferred.Semipermeable membrane 16, as illustrated in FIG. 2 may be fabricatedfrom those materials mentioned above as being suitable for tubularmembers 2 and 12.

One specific embodiment of the wound drain device fabricated inaccordance with this invention and as illustrated in FIG. 2 is asfollows:

Semi-permeable tubing 12 (two tubes):

Composition anisotropic cellulose acetate Cross-section 0.5 cm

Length 10 cm Connector 13:

Composition opaque polyethylene Length 25 cm Collection flask l4:

Composition opaque polyethylene Volume of compartment 15 250 cc Volumeof compartment 17 250 cc Volume of compartment 18 250 cc Diaphragm l9composition styrene-butadiene rubber Semi-permeable membrane 16anisotropic cellulose acetate This device is capable of removing up tocc per day of water from body fluids accumulating in the area ofa woundin a human body. This has been found quite satisfactory for all butuncommonly large surgical incisions, in which case larger tubes and/ormore tubes may be employed to withdraw the necessary amount of bodyliquid from the wound area.

While the invention has been described and illustrated with reference tocertain preferred embodiments thereof, those skilled in the art willappreciate that various modifications, changes, additions, andsubstitutions can be made without departing from the spirit of theinvention. It is intended, therefore, that the invention be limited onlyby the scope of the following claims.

What is claimed is:

I. An evacuator device for the extraction of body fluids, said devicecomprising body fluid receiving means adapted to be inserted into thearea of a wound and comprised of membrane material exhibiting controlledpermeability to water, and means for collecting such water that flows byosmosis across said membrane in a tendency towards osmotic equilibriumwith the environment of the device, said body fluid receiving means andsaid collecting means being filled with a solution of an osmoticallyeffective solute which exhibits an osmotic pressure gradient againstwater, said water collection means including a freely flexible, waterimpermeable diaphragm.

2. The evacuator device as defined by claim 1, wherein said body fluidreceiving means is comprised of elongated tubing.

3. The evacuator device as defined by claim 2, wherein said watercollection means is comprised of a container which is compartmented bymeans of said freely flexible, water impermeable diaphragm.

4. The evacuator device as defined by claim 3, wherein the elongatedtubing communicates with a first compartment of said container, suchfirst compartment and the said tubing being filled with said solution ofan osmotically effective solute which exhibits an osmotic pressuregradient against water, and the said freely flexible, water impermeablediaphragm defining wall means comprising said first compartment.

5. The evacuatordevice as defined by claim 4, wherein the container iscompartmented into three compartments by means ofa membrane exhibitingcontrolled permeability to water and by said freely flexible, waterimpermeable diaphragm.

6. The evacuator device as define by claim 5, wherein the elongatedtubing communicates with a first compartment of said container, suchfirst compartment and the said tubing being filled with said solution ofan osmotically effective solute which exhibits an osmotic pressuregradient against water; the said first compartment being separated fromthe second compartment by wherein the first solution is normal saline.

1. An evacuator device for the extraction of body fluids, said devicecomprising body fluid receiving means adapted to be inserted into thearea of a wound and comprised of membrane material exhibiting controlledpermeability to water, and means for collecting such water that flows byosmosis across said membrane in a tendency towards osmotic equilibriumwith the environment of the device, said body fluid receiving means andsaid collecting means being filled with a solution of an osmoticallyeffective solute which exhibits an osmotic pressure gradient againstwater, said water collection means including a freely flexible, waterimpermeable diaphragm.
 2. The evacuator device as defined by claim 1,whereIn said body fluid receiving means is comprised of elongatedtubing.
 3. The evacuator device as defined by claim 2, wherein saidwater collection means is comprised of a container which iscompartmented by means of said freely flexible, water impermeablediaphragm.
 4. The evacuator device as defined by claim 3, wherein theelongated tubing communicates with a first compartment of saidcontainer, such first compartment and the said tubing being filled withsaid solution of an osmotically effective solute which exhibits anosmotic pressure gradient against water, and the said freely flexible,water impermeable diaphragm defining wall means comprising said firstcompartment.
 5. The evacuator device as defined by claim 4, wherein thecontainer is compartmented into three compartments by means of amembrane exhibiting controlled permeability to water and by said freelyflexible, water impermeable diaphragm.
 6. The evacuator device as defineby claim 5, wherein the elongated tubing communicates with a firstcompartment of said container, such first compartment and the saidtubing being filled with said solution of an osmotically effectivesolute which exhibits an osmotic pressure gradient against water; thesaid first compartment being separated from the second compartment bymeans of the membrane exhibiting controlled permeability to water andsaid second compartment being filled with a second solution of anosmotically effective solute which exhibits an osmotic pressure gradientagainst water, said second solution being more concentrated than thefirst; and the said second compartment being separated from a third,empty compartment by means of the freely flexible, water impermeablediaphragm.
 7. The evacuator device as defined by claim 1, furthercomprising means for attaching the water collector to the body of apatient.
 8. The evacuator device as defined by claim 6, wherein thefirst solution is normal saline.